Method of and apparatus for preventing sparking in dynamo-electric machines.



B. J. BOIGOURT. METHOD OF AND APPARATUS FOR PREVENTING SPARKING IN DYNAMO ELECTRIC MACHINES. APPLICATION FILED JAN 27, 1911.

1,121,065, Patented Dec. 15. 1914.

Wu 3) w 46 7 A? 4 Q x I E Qm/Jera e/ THE NORRIS FETERS Ca. PHOTOVLITHOH WASHINGTON. D. C.

UNITED STATES PATENT QFETCE.

BARENT J. BOICOURT, 0F COLORADO SPRII'IGS, SOLGBADQ, ASSIGIIOPL, BY MESNE.

ASSIGNMENTS, TQ C. & C. ELECTRIC 6 MANUEAGTUFIIIG COMPANY, A COR- PORATION OF NEW JERSEY.

METHOD OF AND APPARATUS FOR PREVENTING SPARRING? IN DYNAEv'IO-ELECTRIC MACHINES.

Application filed January 2'7, 1811.

To all whom it may concern it known that I, Bnnnxr J. Borooon'r, a citizen of the United States, residing at Colorado Springs, Colorado, have invented certain new and useful Improvements in hlethods of and Apparatus for Preventing Sparking in Dynamo-Electric Machines, of which the following is a clear, full, and eX- act description.

The present invention relates to an improyement in dynamo electric machines in the broad sense, that is, either a dynamo for generating current or a motor for utilizing current, and has for its object more particularly the prevention of excessive sparking in such machines under all conditions of operation.

lhe purposes and general theory of the ordinary interpole motor are well understood as for instance in the patents to lVTather #321,990 dated July 14, 1885 and Pfatischer #775,310 dated Nov. 22, 1904-, and need not be more particularly described herein. It is suflicient to mention that interpoles are employed for the purpose of providing an interpole magnetic field for the armature coils undergoing commutation to assist in reversing the currents in said coils. The electro-motive force generated in the armature coils tending to maintain the current in one direction and resist the change in direction thereof I prefer to call the reactance voltage, and the electro-motive force generated in opposition thereto by the interpole field I prefer to call counterreactance voltage. It is desirable for sparkless commutation that this counter-reactance voltage at all times equal in value the reactance voltage or even slightly exceed the same so as to more readily cause a reversal of the current in the armature coils undergoing commutation. The reactance voltage of course depends and varies directly with the armature current and the commutating coils of the interpoles are usually connected in series with the armature in an attempt to vary the magnetism of the interpoles in accordance with the load on the armature and thus generate a counterreactance voltage equal to or superior to the reactance voltage at all times. It has been found however. that these ideal conditions do not occur,-although for small variations Specification of Letters Patent.

Patented Dec. 15, 1914.

Serial No. 605,003.

of armature current the arrangement is fairly satisfactory; but that even with the commutating coils connected in series with the armature, the interpole field and consequently the counter-reactance voltage induced thereby does not vary in strength proportionately to the reactance voltage induced by the armature current, and during heavy overloads bad sparking will occur. This is partly due to the tendency of the interpoles to become magnetically saturated by increased current in the commutating coils and partly due to the effect on the interpole iield of the increased main field distortion caused by increased armature reaction. Consequently good commutation is not obtained with these former interpole machines when the armature current is increased beyond certain limits due to the failure of the interpole field to respond in strength proportionately to the armature current. In the present embodiment of my invention 1 have shown one means for remedying these defects of former interpole motors. In the fozm shown I generate a mag .eto-motive force for the interpole field which varies in one ratio with the armature current for normal loads and which is suddenly jumped up to vary with said armature current in a higher ratio during abnormal loads. If the means for thus accelerating the magnet motive force of interpole field are properly adjusted for the currents to be commutated and are also arr 'ed to act instanthe taneously with. the change of armature current, good commutation can be obtained under all practical conditions.

In the drawings which show the preferred manner in which my invention may be carried out, Figure 1 is a diagrammatic illustration of a direct current shunt-wound motor arranged with my improvement thereon; and Fig. 2 is a diagram of characteristic curves.

Referring first to Fig. 1, 2 indicates the armature motor rotating in the direction of the arrow; 3 and 10 indicate the main field poles for the armature which it is observed are shunt-wound from the main motor circuit 22 and 23. 4 and 4: represent the pole pieces for the interpoles and are wound as shown with main commutating coils 1 and 8 respectively, connected in series with the 7 adapted to be bridged by block 11 armature to provide a definite. number of interpole turns for the armature current.

The usual armature contact brushes are shown at 15 and 15. It will be observed that the interpoles are also wound with auxiliary commutating coils 6 and 9 normally disconnected from any line and there- I auxiliary commutating coils to properly ad-v just their action as may be desired.

The present invention contemplates the use as shown of main commutating coils connected in series with the main motor circuit for normal operation of the motor under ordinary loads and the inclusion "of the auxiliary coinmutating coils in the main motor-circuit during overloads to vary the magnetism of the interpoles as required. In the drawings I have shown diagrammatically merely a preferred form of construction and arrangement of connections for accomplishing these desired results. The main motor circuit 22, 23 is provided with a break formed by separated contacts 12, 12, which may be operated by suitable electro-magnetic means indicated by a solenoid 5 and relay circuit controlling switch 14:. The auxiliary coinmutating coils 6 and 9 are preferably included in a local circuit normally open by separated contacts 13. These connections are thus arranged to show in a simplified way how the motor may be operated for normal loads with only the main commutating coils in series with the armature, and how a sudden overload may be imposed upon the armature and simultaneously the auxiliary commutating coils be added in series to the armature so that theinterpole field may be strengthened to take care of the increased reactance voltage.

hen the block 11 bridges the contacts 12, the motor may be considered as operating under normal load. The main commutating coils l and 8 are-properly proportioned to take care of this normal load and slight variations thereof for sparkless commutation. if it is desired to impose an overloadon the armature, the switch 14% can be opened to allow block 11, to drop away from contacts 12 and bridge contacts 18. This will immediately connect the armature in series w th the main and auxiliary commutating coils, all in a locally closed circuit, which practically short-circuits thearmature. As

is well known short-circuiting the armature generates a great overload of armature current and produces what is known-as a dynamic brake for uicklv stoo in the motor.-

. v, l i z:

In the use of these interpole motors for operating machinery such as planers, it IS the common practice to short-circuit the armature for applying a dynamic brake in this Referri1ig more particularly to Fig. 2, illustrating certain characteristic curves of my interpole motor, line E-S is a measure of amperage and line E-O a measure of voltage. characteristic of the reactance voltage of the armature coils undergoing commutation. The line E-K may be regarded as the characteristic curve of the counter-reactance voltage for any definite number of coils on i the interpoles. The lines ET and EK are drawn in this way to illustrate their changing value relative to one another through different armature loads or amperage. Of course the ideal condition would be to have the line E,K coincide with line E-T, or perhaps gradually diverge there from in an upward direction; in other words, to have the counter-reactance voltage equal but opposite to the reactance voltage at all times with a perhaps slight surplus as before stated. It is observed that line EK on small loads remains fairly close to line ET but on larger loads rapidly departs therefrom. The dotted lines A-B and CD indicate the limits of departure for line E-K relative to line ET before injurious sparking begins. Assuming to be the normal load imposed on the armature, the reactance voltage and the counter-reactance voltage is ZN. The 8 are so pro- F main comiiiutating coils l and portioned as to cause line EK to intersect line at N at normal load so that the widest latitude is given in either direction for the armature current to vary before sparking begins, 4

is-increased beyond 'E-X, the intersection I of EK with CD shows that sparking will begin unless something is done to prevent. it. This preventionis accomplished by changing the character of line E-K to This-is brought about as before stated, by means of the auxiliary commutating coils 6 and 9 on the interpoles. The intersection G of EGH should be directly above intersection I of EI K so that the reactance voltage VVX will be opposed as well-by G\T counter-reactance voltage as by IX counter-reactance voltage, thusallowing a gradual as well as an abrupt increase of the reactanc'e voltage to be injurious sparking.

The diagonal line ET is then If the armature current taken care of for sparlrless commutation by the sudden jump or counter-reactance voltage. The additional commutating coils 6 and 9 are properly proportioned to eiiect this result.

It is obvious that various changes and adaptations of my invention as here illustrated may he made withou departing from the spirit and scope of the iDYQDtiOIl as expressed in the appended claims.

I'Vhat I claim as new is 1. The combination with a dynamo electric machine having an armature, main commutating coils and normally deenergized auxiliary commutating coils, of means for connecting the main commutating coils in the main motor circuit for normal operation, and for disconnecting said main coils and then connecting the armature, the main and the auxiliary commutating coils in a local closed circuit for braking.

In a direct current dynamo electric machine in combination, an armature, main ield poles therefor, interpoles, main commutating coils on said interpoles arranged to be ener ized during the operation of the machine, auxiliary commutating coils on said interpoles, and means for energizing and deenergizing said auxiliary commutating coils for varying the magnetism of said interpoles as required.

3. In a direct current dynamo electric machine in combination, an armature, main field poles therefor, interpoles, main commutating coils on said interpolcs arranged to be connected in series with said armature during the operation of the machine, auxiliary commutating coils on said interpoles, and means for energizing and deenergizing said auxiliary commutating coils for varying the magnetism of said interpoles in greater degree than the changes caused by a variation of armature current flowing in said main commutating coils.

4:. In a. direct current dynamo electric machine in combination, an armature, main field poles therefor, interpoles, main commutating coils on said interpoles arranged to be connected in series with said armature during the operation of the machine, auxiliary commutating coils on said interpoles, and means for connecting and disconnecting said auxiliary commutating coils with and from said armature, for varying the magnetism of said interpoles in greater degree than the changes caused by a variation of armature current flowing in said main commutating coils.

5. In a direct current dynamo electric machine in combination, an armature, main field poles therefor, interpoles, main commutating coils on said interpoles arranged to be connected in series with said armature during the operation of tie machine, auxiliary commutating coils on said interpoles,

and electromagneticallyoperated means for connecting and disconnecting said auxiliary commutating coils with and from said armature, for varying the magnetism of said interpoles in greater degree than the changes caused by a variation 01 armature current flowing in said main commutating coils.

6. In a direct current dynamo electric machine in combination, an armature, main field poles therefor, inter-poles, main commutating coils on said interpoles arranged to he connected in series with said armature during the operation of the machine, auX- iliar commutating coils on said interpoles, and means for connecting said auxiliary commutating coils in series with said armature and disconnecting the same therefrom for varying the magnetism of said interpoles in greater degree than the changes caused by a variation of armature current flowing in said main commutating coils.

7. In a direct current dynamo electric machine in combination, an armature, main field poles therefor, inter-poles, main and auxiliary commutating coils on said interpoles, said main commutating coils arranged to be connected in series with said armature during normal operation of said motor, and electromagnetically operated means for connecting said armature, main and auxiliary commutating coils in a locally closed circuit for braking.

S. The method of operating an interpole electric machine through various loads without excessive sparking, which consists in generating a magneto-motive force for the interpole field, which varies with the armature current of said machine in one ratio for normal loads on said armature, and at a time no later than the occurrence of an overload upon said armature, jumping said ma neto-motive force suddenly to an increased ratio with respect to said armature current.

9. The method of operating an interpole electric machine through various loads without excessive sparking, which consist-s in generating a magneto-motive force for the interpole field, which varies with the armature current of said machine in one ratio for normal loads on said armature, and at a time no later than the occurrence of an overload upon said armature, jumping said magneto-motive force suddenly to an increased ratio with respect to said armature current and at a time no later than the cessation of overload upon said armature, jumping said magneto-motive force back to its normal ratio with respect to said armature current.

10. The method of operating an interpole electric machine through various loads without excessive sparking, which consists in generating a magneto-motive force for the interpole field, which varies with the armature current of said machine in one ratio for normal loads on said. armature, imposing an overload upon said armature and at a time no later than the occurrence of said overload jumping said 1nagneto motive force suddenly to an increased ratio with respect to said armature current.

11. The method of operating an interpole electric machine through various loads Without excessive sparking, which consists in. generating a magneto-motive force for the interpole field, which varies With the armature current of said machine in one ratio for normal loads on said armature, imposing an overload upon said armature and at a time no laterthan the occurrence of said overload jumping said magnetomotive force suddenly to an increased ratio with respect to said armature current, removing the overload from said armature and at a time no later than the removal of said overload jumping said magneto-motive force back to its normal ratio with respect to said armature.

12. The method of operating an interpole electric machine through various loads Without excessive sparking, Which consists in conducting the armature current through a definite number of turns about said interpole to generate a magneto-motive force for said interpcle field, and at a time no later than the occurrence of an overload upon said armature conducting said armature current through an additional number of turns about said interpole.

13. The method of operating an interpole electric machine through various loads Without excessive sparking, which consists in conducting the armature current through a definite number of turns about said interpole to generate a magneto-motive force for said interpole field, imposing an overload upon saio armature and at a time no later than the occurrence of said overload con ducting said armature current through an additional number of turns about said interpole.

Signed at Colorado Springs this 2nd day of May 1910.

BARENT J. BOIGOURT.

lVitnesses:

R. E. JOHNSON, v FRANK H. DUNNIGGTON.

Copiesof this patent may be obtained for five cents each. by addressing the. Commissioner of Patents, Washington, I). C. 

